Magnetic memory devices in which a magnetoresistive effect element is formed on a semiconductor substrate have been offered.
The above-described magnetoresistive effect element comprises a structure in which, for example, a storage layer, a tunnel barrier layer, a reference layer and a shift cancelling layer are stacked in this order. The shift cancelling layer is used for cancelling a magnetic field applied from the reference layer to the storage layer. In existing magnetoresistive effect elements, for example, since a shift cancelling layer is stacked on a reference layer, a thick shift cancelling layer is needed. Therefore, the total thickness (height) of a stack structure becomes great.
The stack structure is formed by processing a stack film by ion beam etching (IBE). In this case, the stack film is processed by applying an ion beam in an oblique direction. Therefore, when the ratio of the height of the stack structure to the width of the space between the stack structures adjacent to each other is high, it is difficult to process the stack film by IBE due to a shadow effect. For example, the limit value of the above-described ratio is about one. As a magnetoresistive effect element is further miniaturized, the above-described ratio becomes greater, and thus it becomes more difficult to process the stack film by IBE.
Further, a structure in which either a shift cancelling layer or a reference layer is provided on the lower layer side of a storage layer has been offered. In a case where this structure is adopted, it is necessary to combine IBE and reactive ion etching (RIE) to form a stack structure. However, it is difficult to perform a precise etching control by RIE.
As described above, as a magnetic memory device is miniaturized, it becomes difficult to form a stack structure accurately.
Therefore, there is demand for a magnetic memory device with an accurate stack structure and for a method of manufacturing such a magnetic memory device.